Béla Lugosi
— Dr. Melcher/ Monsieur Colomb
Clayton Moore
— FBI Agent Richard ‘Dick’ Martin
Joan Barclay
— Alice Saunders
George Pembroke
— Dr. William Saunders
Robert Frazer
— Amos Hanlin
Robert Fiske
— Phillip Wallace
Irving Mitchell
— John Van Dyke
Edward Peil Sr.
— Ryder
Kenneth Harlan
— FBI Chief Colton
Max Hoffman Jr.
— Kearney
Joseph Eggenton
— Stevens
I. Stanford Jolley
— The Dragon
Frank Melton
— FBI Agent